Resin coated metal sheet

ABSTRACT

A resin coated metal sheet includes a metal sheet, a first resin coating layer formed on one main surface of the metal sheet and formed of a resin material whose difference between a heat quantity of crystallization and a heat quantity of fusion after being laminated to the metal sheet is 0 J/g to 20 J/g on a unit weight basis, and a second resin coating layer formed on another main surface of the metal sheet.

TECHNICAL FIELD

This disclosure relates to a resin coated metal sheet in which a metalsheet has resin coating layers on both sides thereof.

BACKGROUND

In general, metal containers are broadly divided into two-piece cans andthree-piece cans. The two-piece can refers to a metal containerconsisting of two parts of a can body integral with a can bottom and alid body. The three-piece can refers to a metal container consisting ofthree parts of a can barrel, an upper lid, and a bottom lid. Althoughthe can body of the two-piece can has a fine appearance because it hasno seamed part (welded part), it in general requires a high degree ofworking. In contrast, although the can barrel of the three-piece can isinferior in appearance as compared to the can body of the two-piece canbecause it has seamed parts, it does not in general require a highdegree of working. Given these circumstances, there is a tendency thatthe two-piece cans are used for expensive small-volume metal containersand the three-piece cans are used for inexpensive large-volume metalcontainers.

Among the two-piece cans, as a metal material for a can body of atwo-piece can that has a high degree of working in drawing and has ahigh degree of stretching in a can height direction, that is, atwo-piece can having a high degree of working, a soft metal materialsuch as aluminum, which is expensive and has a large sheet thickness, isused, and a steel sheet such as tinplate or tin-free steel, which isinexpensive and has a small sheet thickness, is little used. The reasonis that while forming methods having a high degree of working such asthe drawing method and the draw and ironing (DI) method are hard to beadopted to the steel sheet, the impact forming method having a highdegree of working can be applied to the soft metal material. Examples ofthe two-piece can having a high degree of working include an aerosolcan.

For a two-piece can having a low degree of working, technologies havebeen developed for manufacturing can bodies by the drawing method andthe DI method using as a material a resin coated metal sheet in which ametal sheet has resin coating layers on both sides thereof (see JapaneseExamined Patent Application Publication No. 7-106394, Japanese PatentNo. 2526725 and Japanese Patent Application Laid-open No. 2004-148324).To allow treatment to improve the designability of a can body such asprinting treatment, technologies have also been developed to add a whitepigment to a resin coating layer positioned outside a metal containerafter forming (Japanese Patent Application Laid-open Nos. 8-169098 and2004-130536).

We investigated whether a can body of a two-piece can having a highdegree of working can be manufactured using a steel sheet that isinexpensive and has high strength despite of its small sheet thickness,a two-piece can having a high degree of working can be provided at alower price. We then manufactured a can body of a two-piece can having ahigh degree of working using a resin coated metal sheet and performedheat treatment at a temperature close to the melting point of the resincoating layer to increase adhesion between the resin coating layer and ametal sheet after forming, the laminatability of the back side resincoating layer positioned inside a metal container after forming, and thedesignability of the front side resin coating layer positioned outsidethe metal container after forming. As a result, we found that ablack-spot shaped pattern was formed on the front side resin coatinglayer after heat treatment and that appearance defects were caused bythe heat treatment. Given this situation, to manufacture a can body of atwo-piece can having a high degree of working using a resin coated metalsheet, it is required that no appearance defect is caused by heattreatment.

SUMMARY

We found that the appearance defects are caused by heat treatmentbecause a residual stress within the resin coating layer that hasdeveloped during forming is relaxed by heat treatment and the resincoating layer becomes deformed unevenly to form uneven distribution of apigment. Based on this finding, we further considered that the residualstress of the resin coating layer after forming can be reduced bycontrolling the degree of crystallinity of the resin coating layer,thereby reducing the uneven deformation of the resin coating layer andthe occurrence of appearance defects caused by heat treatment.

Our resin coated metal sheet can include: a metal sheet, a first resincoating layer that is formed on onemain surface of the metal sheet andformed of a resin material whose difference between a heat quantity ofcrystallizaqtion and a heat quantity of fusion after being laminated tothe metal sheet is within a range of 0 J/g to 20 J/g on a unit weightbase; and a second resin coating layer formed on another main surface ofthe metal sheet.

The resin coated metal sheets can reduce the residual stress of theresin coating layer positioned outside a container after forming,thereby reducing the occurrence of appearance defects caused by heattreatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating the constitution of an exampleof our resin coated metal sheets.

FIG. 2 is a sectional view illustrating the constitution of amodification to the resin coated metal sheet illustrated in FIG. 1.

REFERENCE SIGNS LIST

-   1 Resin coated metal sheet-   2 Metal sheet-   3,4 Resin coating layer

DETAILED DESCRIPTION

The following describes a resin coated metal sheet with reference to theaccompanying drawings.

FIG. 1 is a sectional view illustrating the constitution of one of ourresin coated metal sheets. FIG. 2 is a sectional view illustrating theconstitution of a modification to the resin coated metal sheetillustrated in FIG. 1. As illustrated in FIG. 1, this resin coated metalsheet 1 includes a metal sheet 2, a resin coating layer 3 formed on thefront side of the metal sheet 2, and a resin coating layer 4 formed onthe back side of the metal sheet 2. The resin coating layer 3 and theresin coating layer 4 are positioned outside and inside a metalcontainer after forming, respectively.

The metal sheet 2 is formed of a steel sheet such as tinplate ortin-free steel. With regard to the tinplate, one having a plating amountof 0.5 to 15 g/m² may be used. The tin-free steel may have on itssurface a chromium metal layer with an adhesion amount of 50 to 200mg/m² and a chromium oxide layer with an adhesion amount of 3 to 30mg/m² on a chromium metal layer basis. The steel sheet, which is notlimited in particular in its type, so long as it can be formed into anintended shape, is preferably one based on the following components andmanufacturing methods:

-   -   (1) One obtained by using low-carbon steel with a carbon (C)        amount of about 0.01 to 0.10% and performing recrystallization        annealing by box annealing.    -   (2) One obtained by using low-carbon steel with a C amount of        about 0.01 to 0.10% and performing recrystallization annealing        by continuous annealing.    -   (3) One obtained by using low-carbon steel with a C amount of        about 0.01 to 0.10% and performing recrystallization annealing        by continuous annealing and overaging treatment.    -   (4) One obtained by using low-carbon steel with a C amount of        about 0.01 to 0.10% and performing recrystallization annealing        by box annealing or continuous annealing, and then performing        secondary cold rolling (double reduced (DR) rolling).    -   (5) One obtained by using interstitial free (IF) steel in which        elements such as Nb and Ti interstitially fixing dissolved C are        added to extra-low-carbon steel with a C amount of about 0.003%        or less and performing recrystallization annealing by continuous        annealing.

The mechanical property of the steel sheet is not limited in particularso long as the steel sheet can be formed into an intended shape, but tonot impair workability and maintain sufficient can body strength, asteel sheet whose yield strength YP is about 220 MPa or more and 580 MPaor less is preferably used. With regard to the Lankford (r-value) as anindicator of plastic anisotropy, one with a value of 0.8 or more ispreferable, and with regard to the intra-plane anisotropy Δr of ther-value, one with its absolute value of 0.7 or less is preferable. Thesheet thickness of the steel sheet can be appropriately set based on theshape of an intended can and necessary can body strength. In view ofreducing an increase in the cost of the steel sheet and the can body, asteel sheet with a sheet thickness of about 0.15 to 0.4 mm is preferablyused.

The resin coating layers 3 and 4 are formed of a resin materialcontaining 90 mol % or more ethylene terephthalate unit, preferably 92mol % or more. A resin material with ethylene terephthalate unit beingless than 90 mol % is not preferable because the resin material issubjected to heat treatment at nearly the melting point after forming,which causes thermal degradation. Without impairing its heat resistanceand workability, the resin material may be copolymerized with othercomponents such as a dicarboxylic acid component and a glycol component.Examples of the dicarboxylic acid include: aromatic dicarboxylic acidssuch as isophthalic acid, naphthalene dicarboxylic acid, diphenyldicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, and phthalic acid;aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipicacid, sebacic acid, dimer acid, maleic acid, and fumaric acid; alicyclicdicarboxylic acid such as cyclohexane dicarboxylic acid; andoxycarboxylic acid such as p-oxybenzoic acid. Examples of the glycolcomponent include: aliphatic glycols such as propanediol, butanediol,pentanediol, hexanediol, and neopentyl glycol; alicyclic glycol such ascyclohexane dimethanol; aromatic glycols such as bisphenol A andbisphenol S; and diethylene glycol. Two or more of these dicarboxylicacid components and the glycol components may be used in combination.

The resin material forming the resin coating layers 3 and 4 is notlimited in its manufacturing method. The resin material can bemanufactured by, for example, (1) a method in which terephthalic acid,ethylene glycol, and a copolymerization component are subjected to anesterification reaction, and then the resultant reaction product ispolycondensed to obtain copolyester and (2) a method in which dimethylterephthalate, ethylene glycol, and a copolymerization component aresubjected to a transesterification reaction, and then the resultantreaction product is polycondensed to obtain copolyester. Inmanufacturing copolyester, additives such as fluorescent brighteningagents, antioxidants, thermal stabilizers, UV absorbers, and antistaticagents may be added as needed. The addition of a fluorescent brighteningagent is effective in improving whiteness.

The time period during which the resin coating layers 3 and 4 are heldat a temperature of not less than their melting point during laminationto the metal sheet 2 is preferably within a range of 1 to 30milliseconds. Pressing pressure during the lamination is not limited inparticular, but the surface pressure is preferably within a range of 9.8to 294 N (1 to 30 kgf/cm²). When the surface pressure is lower than thisrange, even when the temperature of the boundary surface between themetal sheet 2 and the resin coating layers 3 and 4 is not less than themelting point, the resin coating layers 3 and 4 melt insufficiently,because the time period during which the temperature is not less thanthe melting point is short, which may fail to achieve sufficientadhesion between the resin coating layers 3 and 4 and the metal sheet 2.When the surface pressure is higher than this range, the deposition ofthe resin coating layers 3 and 4 may occur. Melt extrusion laminationmay be applied in which a melted resin material, instead of thefilm-like resin material, is laminated to the surface of the metal sheet2.

The resin coating layer 3 is formed of a resin material whose differencebetween the heat quantity of crystallization and the heat quantity offusion after being laminated to the metal sheet 2 is 0 J/g or more and20 J/g or less, preferably 0 J/g or more and 18 J/g or less, and morepreferably 0 J/g or more and 14 J/g or less, on a unit weight basis. Theheat quantity of crystallization and the heat quantity of fusion can bemeasured using a differential scanning calorimetry (DSC). The differencebetween the heat quantity of crystallization and the heat quantity offusion gives an indicator of the degree of crystallinity of the resincoating layer 3 after lamination. When the difference between the heatquantity of crystallization and the heat quantity of fusion is 0 J/g,the resin coating layer 3 is in an amorphous state, the degree ofcrystallinity of the resin coating layer 3 is nearly zero, and aresidual stress after forming is low. For this reason, no appearancedefect is caused by heat treatment. When the difference between the heatquantity of crystallization and the heat quantity of fusion exceeds 20J/g, the degree of crystallinity of the resin coating layer 3 is high,and the residual stress after forming is high. For this reason,appearance defects are caused by heat treatment.

The degree of crystallinity of the resin coating layer 3 can becontrolled by controlling the degree of orientation and melting point ofthe resin coating layer 3 before lamination and lamination conditions(steel sheet heating temperature, nip pressure, time until water coolingafter lamination, cooling temperature after lamination, and line speed).Specifically, by increasing the heating temperature of the metal sheet 2during lamination, the degree of crystallinity of the resin coatinglayer 3 can be reduced. The heating temperature of the metal sheet 2,which differs by the melting point and degree of crystallinity beforelamination of the resin coating layer 3, is higher than the meltingpoint of the resin coating layer 3 by 10 to 50° C. By reducing the nippressure, the cooling effect of the resin coating layer 3 by the nip isreduced, thereby reducing the degree of crystallinity of the resincoating layer 3. By reducing the time until water cooling afterlamination, the crystallization of the resin coating layer 3 during thecooling process after lamination can be reduced, thereby reducing thedegree of crystallinity of the resin coating layer 3. The time untilwater cooling after lamination, which depends on a line speed, is 0.5seconds to 10 seconds. By increasing the line speed, the degree ofcrystallinity of the resin coating layer 3 can be reduced even under thesame conditions as to heating roll temperature. This is because theinfluence of natural cooling or the like after it is heated until it islaminated diminishes.

The melting point of the resin coating layer 3 is 240° C. or more and254° C. or less, preferably 242° C. or more and 252° C. or less, andmore preferably 244° C. or more and 250° C. or less. When the meltingpoint of the resin coating layer 3 is less than 240° C., the resincoating layer 3 is likely to soften through surface sliding duringworking, the working heat generation of the metal sheet 2 or the like,which may lead to the occurrence of a scrape on the surface of the resincoating layer 3 or the breakage thereof. When the melting point of theresin coating layer 3 exceeds 254° C., the degree of crystallinity ofthe resin coating layer 3 increases, and it may fail to allow working ata high degree of working.

It is preferable that the intrinsic viscosity (IV) of the resin coatinglayer 3 is 0.55 dl/g or more and 0.90 dl/g or less, preferably 0.58 dl/gor more and 0.80 dl/g or less, and more preferably 0.59 dl/g or more and0.78 dl/g or less. When the intrinsic viscosity of the resin coatinglayer 3 is less than 0.55 dl/g, the melt viscosity of the resin coatinglayer 3 is low, thereby making uneven deformation of the resin coatinglayer 3 likely to occur during heat treatment. When the intrinsicviscosity of the resin coating layer 3 exceeds 0.90 dl/g, filmformability degrades. The intrinsic viscosity (IV) of a laminated resincan be adjusted by changes in polymerization conditions (polymerizationcatalyst amount, polymerization temperature, polymerization time, or thelike) and the solid phase polymerization method in an inert gasatmosphere such as nitrogen or in a vacuum following meltpolymerization.

The resin coating layer 3 is required to be white to allow treatment toimprove designability such as printing treatment. For this reason, theresin coating layer 3 preferably contains titanium oxide in an amount of8 wt % or more and 30 wt % or less, preferably 10 wt % or more and 25 wt% or less, and more preferably 12 wt % or more and 20 wt % or less. Whenthe content of the titanium oxide is less than 8 wt %, sufficientwhiteness cannot be ensured after working. When the content of thetitanium oxide exceeds 30 wt %, forming at a high degree of workingcauses problems with the adhesion between the metal sheet 2 and theresin coating layer 3 and workability.

With regard to titanium oxide added to the resin coating layer 3, whichis not limited in particular, one whose purity of rutile type titaniumoxide is 90% or more is preferably used. When the purity of rutile typetitanium oxide is less than 90%, the dispersibility of titanium oxide ispoor when it is mixed with the resin material, which may result in areduced molecular weight of the resin material. A method of addingtitanium oxide may use various methods listed in (1) to (3) below. Whenadding titanium oxide using the method (1), titanium oxide is preferablyadded to a reaction system as slurry dispersed in glycol. The thicknessof the resin coating layer 3 with titanium oxide added is preferable tobe 10 to 40 μm, preferably 12 to 35 μm, and more preferably 15 to 25 μmto ensure the whiteness after working. When the thickness of the resincoating layer 3 is less than 10 μm, cracking is likely to develop in theresin coating layer 3 during working. The thickness of the resin coatinglayer 3 exceeding 40 μm gives excessive quality, which is uneconomical.

(1) A method in which titanium oxide is added before the termination ofthe transesterification reaction or the esterification reaction orbefore the start of the polycondensation reaction in the synthesis ofcopolyester;

(2) A method in which titanium oxide is added to copolyester and meltkneading is performed; and

(3) A method in which in the methods (1) and (2), master pellets towhich a large amount of titanium oxide is added are manufactured andkneaded with copolyester that contains no particle, to allow apredetermined amount of titanium oxide to be contained.

As illustrated in FIG. 2, the resin coating layer 3 may have athree-layer structure of an outermost layer (an upper layer) 3 a, anintermediate layer 3 b, and a lowermost layer (a lower layer) 3 c. Inthis case, the film thickness of the outermost layer 3 a and thelowermost layer 3 c may be 1 μm or more and 5 μm or less, preferably 1.5μm or more and 4 μm or less, and more preferably 2 μm or more and 3 μmor less, and the film thickness of the intermediate layer 3 b may be 6μm or more and 30 μm or less, preferably 8 μm or more and 25 μm or less,and more preferably 10 μm or more and 20 μm or less. The outermost layer3 a and the lowermost layer 3 c may contain titanium oxide in an amountof 0 wt % or more and 2 wt % or less, and the intermediate layer 3 b maycontain titanium oxide in an amount of 10 wt % or more and 30 wt % orless.

When the film thickness of the outermost layer 3 a and the lowermostlayer 3 c is less than 1 μm, a scrape develops in the resin coatinglayer 3, or the luster of the surface of the resin coating layer 3cannot be ensured sufficiently. When the film thickness of the outermostlayer 3 a and the lowermost layer 3 c exceeds 5 μm, it is required toincrease the film thickness of the intermediate layer 3 b containingtitanium oxide or increase the content of titanium oxide to ensure thewhiteness, which is unfavorable in economy and workability. It ispreferable that the difference in the melting points among the outermostlayer 3 a, the intermediate layer 3 b, and the lowermost layer 3 c is10° C. or less, preferably 6° C. or less, and more preferably 3° C. orless. When the difference in the melting points among the layers exceeds10° C., appearance defects are likely to be caused by unevendisplacement (flowing), because the melted state differs significantlybetween the layers because of heat treatment.

To reduce the occurrence of a scrape and breakage in the resin coatinglayer 3 during forming at a high degree of working, a wax component maybe applied or added to the resin coating layer 3. With regard to the waxcomponent to be applied or added, which is not limited in particular,organic lubricants and inorganic lubricants can be applied. When the waxcomponent is applied to the resin coating layer 3, preferably used arealiphatic waxes having a melting point of 30° C. or more such asstraight-chain aliphatic series such as paraffin and fatty acid esters.When the wax component is added to the resin coating layer 3, preferablyused are fatty acids and fatty acid esters such as stearic acid,stearate, palmitic acid, and palmitate, which are favorable incompatibility with a polyester resin.

The application amount of the wax component is preferably 20 to 80mg/m². When the application amount of the wax component is less than 20mg/m², the lubricating effect reduces, which is unfavorable. When theapplication amount of the wax component exceeds 80 mg/m², the waxcomponent is excessive, and the wax component remains as a solid contentin a mold in the manufacture of cans, thereby inhibiting canmanufacturability. The addition amount of the wax component ispreferably 0.01 wt % to 5 wt %. When the addition amount of the waxcomponent is less than 0.01 wt %, the lubricating effect reduces, whichis unfavorable. When the addition amount of the wax component exceeds 5wt %, transfer of the wax component or the like occurs when the resincoating layer 3 is wound in a roll shape, which will be problematic.

The resin coating layer 4 is preferably formed of a resin material whosedifference between the heat quantity of crystallization and the heatquantity of fusion after being laminated to the metal sheet 2 is 0 J/gor more and 10 J/g or less on a unit weight basis. When the differencebetween the heat quantity of crystallization and the heat quantity offusion is 0 J/g, the resin coating layer 4 is in an amorphous state, thedegree of crystallinity of the resin coating layer 4 is nearly zero, anda residual stress after forming also reduces. When the differencebetween the heat quantity of crystallization and the heat quantity offusion exceeds 10 J/g, the degree of crystallinity of the resin coatinglayer 4 is high, and the residual stress after forming is high. For thisreason, cracking develops in the resin coating layer 4, therebydegrading corrosion resistance. The degree of crystallinity of the resincoating layer 4, in the same manner as the crystallinity of the resincoating layer 3, can be controlled by controlling the degree oforientation and melting point of the resin coating layer 4 beforelamination and lamination conditions (temperature, nip pressure, andcooling time and temperature).

The resin coating layer 4 is preferably formed of a resin materialhaving a melting point lower than the melting point of the resin coatinglayer 3 by 4° C. or more and 20° C. or less, preferably 6° C. or moreand 14° C. or less. When the melting point of the resin coating layer 4is lower than the melting point of the resin coating layer 3 by lessthan 4° C., the resin coating layer 4 does not melt sufficiently throughheat treatment after working, thereby resulting in imperfect repair ofminute physical flaws or the like along with working. When the meltingpoint of the resin coating layer 4 is lower than the melting point ofthe resin coating layer 3 by more than 20° C., the resin coating layer 4melts excessively through heat treatment after working, causing thermaldegradation to impair laminatability.

EXAMPLES

Using T3CA TFS (tin free steel, Cr metal layer: 120 mg/m², Cr oxidelayer: 10 mg/m² on a Cr metal basis) with a thickness of 0.23 mm as ametal sheet, the resin coating layers of Examples 1 to 23 andComparative Examples 1 to 10 listed in Tables 1 to 3 below were formedon both sides of the metal sheet using the film laminate method (thefilm thermocompression bonding method). Specifically, with the metalsheet heated to a temperature higher than the melting point of the resincoating layer by 20° C., the film-shaped resin coating layer prepared bythe biaxial drawing method using nip rolls was thermocompressed onto themetal sheet and then cooled through water cooling of 5 seconds or less,thereby applying the resin coating layers to both sides of the metalsheet. A resin coating layer (an outer resin layer) containing a whitepigment was laminated to the front side of the metal sheet positionedoutside a container after forming, and a resin coating layer (an innerresin layer) containing no white pigment was laminated to the back sideof the metal sheet positioned inside the container. For the obtainedresin coated metal sheet, measured were the adhesion amount of a waxcomponent (a wax application amount), the intrinsic viscosity (IV) ofthe resin coating layer, the melting point of the resin coating layer,the heat quantity of crystallization of the resin coating layer, and theheat quantity of fusion of the resin coating layer, using the methodslisted below. For the outer resin layer, its whiteness was measured. Themeasurement results are listed in Tables 1 to 3 below.

(1) Adhesion Amount of Wax Component

Measured were the weights of the resin coated metal sheet before theapplication and after the application of the wax component, to calculatethe weight difference of the resin coated metal sheet between before andafter the application of the wax component, as the adhesion amount ofthe wax component.

(2) Intrinsic Viscosity (IV)

A measurement was carried out by the method listed in JIS K7367-5 andwith a concentration of 0.005 g/ml in o-chlorophenol at 35° C. todetermine the intrinsic viscosity by a formula: intrinsicviscosity=(T−T₀)/(T₀×c). In the formula, c denotes a concentrationrepresenting a resin concentration per 100 ml of a solution in terms ofthe number of grams, and T_(o) and T denote the times of flow of asolvent and a resin solution, respectively, within a capillary typeviscometer.

(3) Melting Point of Resin Coating Layer

Using a differential scanning calorimetry apparatus, measured was anendothermic peak when the temperature of the resin coating layer beforelamination was raised from room temperature to 290° C. at a rate oftemperature rise of 10° C./min, to determine the peak temperature of theendothermic peak measured at 200 to 280° C. as the melting point of theresin coating layer.

(4) Heat Quantity of Crystallization and Heat Quantity of Fusion

The resin coating layer was removed from the resin coated metal sheetwith diluted hydrochloric acid, and washed sufficiently with distilledwater to dry. Using a differential scanning calorimetry apparatus,measured was an exothermic peak and an endothermic peak when thetemperature of the resin coating layer was raised from −50° C. to 290°C. at a rate of temperature rise of 10° C./min. The heat quantity ofcrystallization was calculated from the area of the exothermic peakmeasured at 100 to 200° C., and the heat quantity of fusion wascalculated from the area of the endothermic peak measured at 200 to 280°C. For the outer resin layer, with a weight excluding the content oftitanium oxide as a resin amount, the heat quantity of crystallizationand the heat quantity of fusion per unit resin weight were calculated.

(5) Whiteness

Using a spectral color difference meter, the whiteness of the resincoating layer 3 of the resin coated metal sheet was evaluated by themethod listed in JIS 28722. The L-value of the Hunter Lab valuesmeasured under observation conditions with a measurement area of 30 mmdia., a measurement light source of C condition, and a field of view of2° with respect to the measurement light source was determined to be thewhiteness.

TABLE 1 Outer resin layer Upper layer Main Another Melting TiO2 Film Waxapplica- Wax addi- component component point amount thickness tionamount Added tion amount [mol %] [mol %] [° C.] [wt %] [μm] Wax type[mg/m2] wax type [wt %] Example 1 — — — — — — — — — Example 2 EthyleneEthylene 240 5 2 — — — — terephthalate 94 isophthalate 6 Example 3Ethylene Ethylene 254 0 2 — — — — terephthalate 98 isophthalate 2Example 4 Ethylene Ethylene 247 0 2 — — — — terephthalate 96isophthalate 4 Example 5 Ethylene Ethylene 247 0 2 Paraffin wax 40 mg/m2— — terephthalate 96 isophthalate 4 Example 6 Ethylene Ethylene 254 0 2Paraffin wax 40 mg/m2 — — terephthalate 98 isophthalate 2 Example 7Ethylene Ethylene 247 0 2 Paraffin wax 40 mg/m2 — — terephthalate 96isophthalate 4 Example 8 Ethylene Ethylene 247 0 2 Paraffin wax 60 mg/m2— — terephthalate 96 isophthalate 4 Example 9 Ethylene Ethylene 247 0 2Paraffin wax 40 mg/m2 — — terephthalate 96 isophthalate 4 Example 10Ethylene Ethylene 247 0 2 Paraffin wax 40 mg/m2 — — terephthalate 96isophthalate 4 Example 11 Ethylene Ethylene 247 0 2 Paraffin wax 40mg/m2 — — terephthalate 96 isophthalate 4 Example 12 EthyleneCyclohexane 246 0 2 Paraffin wax 40 mg/m2 — — terephthalate 97dimethylene terephthalate 3 Example 13 Ethylene Ethylene 247 0 1Paraffin wax 40 mg/m2 — — terephthalate 96 isophthalate 4 Example 14Ethylene Ethylene 247 0 5 Paraffin wax 40 mg/m2 — — terephthalate 96isophthalate 4 Example 15 Ethylene Ethylene 247 0 5 Paraffin wax 40mg/m2 Stearic acid 0.1 terephthalate 96 isophthalate 4 Example 16Ethylene Ethylene 247 0 5 Paraffin wax 40 mg/m2 Stearic acid 2  terephthalate 96 isophthalate 4 Example 17 Ethylene Ethylene 247 0 5Paraffin wax 40 mg/m2 Stearic acid 5   terephthalate 96 isophthalate 4Example 18 Ethylene Ethylene 247 0 5 Paraffin wax 40 mg/m2 Stearic acid1.5 terephthalate 96 isophthalate 4 Example 19 Ethylene Ethylene 247 0 5Paraffin wax 40 mg/m2 — terephthalate 96 isophthalate 4 Example 20Ethylene Ethylene 247 0 5 Paraffin wax 40 mg/m2 — — terephthalate 96isophthalate 4 Example 21 Ethylene Ethylene 247 0 1 Paraffin wax 40mg/m2 — — terephthalate 96 isophthalate 4 Example 22 Ethylene Ethylene247 0 2 Paraffin wax 40 mg/m2 — — terephthalate 96 isophthalate 4Example 23 Ethylene Ethylene 247 0 2 Butyl 40 mg/m2 — — terephthalate 96isophthalate 4 stearate Outer resin layer Intermediate layer Lower layerFilm Film Main Another Melting TiO2 thick- Main Another Melting TiO2thick- component component point amount ness component component pointamount ness [mol %] [mol %] [° C.] [wt %] [μm] [mol %] [mol %] [° C.][wt %] [μm] Example 1 Ethylene Ethylene 230 20 20 — — — — —terephthalate 89 isophthalate 11 Example 2 Ethylene Ethylene 240 25 18Ethylene Ethylene 240 5 2 terephthalate 94 isophthalate 6 terephthalate94 isophthalate 6 Example 3 Ethylene Ethylene 254 25 18 EthyleneEthylene 254 0 2 terephthalate 98 isophthalate 2 terephthalate 98isophthalate 2 Example 4 Ethylene Ethylene 247 20 18 Ethylene Ethylene247 0 2 terephthalate 96 isophthalate 4 terephthalate 96 isophthalate 4Example 5 Ethylene Ethylene 247 20 18 Ethylene Ethylene 247 0 2terephthalate 96 isophthalate 4 terephthalate 96 isophthalate 4 Example6 Ethylene Ethylene 244 20 18 Ethylene Ethylene 254 0 2 terephthalate 95isophthalate 5 terephthalate 98 isophthalate 2 Example 7 EthyleneEthylene 247 20 18 Ethylene Ethylene 247 0 2 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 8 EthyleneEthylene 247 20 18 Ethylene Ethylene 247 0 2 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 9 EthyleneEthylene 247 9 38 Ethylene Ethylene 247 0 2 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 10 EthyleneEthylene 247 20 16 Ethylene Ethylene 247 0 2 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 11 EthyleneEthylene 247 20 18 Ethylene Ethylene 247 0 2 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 12 EthyleneCyclohexane 246 20 18 Ethylene Cyclohexane 246 0 2 terephthalate 97dimethylene terephthalate 97 dimethylene terephthalate 3 terephthalate 3Example 13 Ethylene Ethylene 247 20 18 Ethylene Ethylene 247 0 1terephthalate 96 isophthalate 4 terephthalate 96 isophthalate 4 Example14 Ethylene Ethylene 247 25 10 Ethylene Ethylene 247 0 5 terephthalate96 isophthalate 4 terephthalate 96 isophthalate 4 Example 15 EthyleneEthylene 247 25 10 Ethylene Ethylene 247 0 5 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 16 EthyleneEthylene 247 25 10 Ethylene Ethylene 247 0 5 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 17 EthyleneEthylene 247 20 10 Ethylene Ethylene 247 0 5 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 18 EthyleneEthylene 247 25 10 Ethylene Ethylene 247 0 5 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 19 EthyleneEthylene 247 25 10 Ethylene Ethylene 247 0 5 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 20 EthyleneEthylene 247 20 30 Ethylene Ethylene 247 0 5 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 21 EthyleneEthylene 247 20 8 Ethylene Ethylene 247 0 1 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 22 EthyleneEthylene 247 20 8 Ethylene Ethylene 247 0 2 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Example 23 EthyleneEthylene 247 20 18 Ethylene Ethylene 247 0 2 terephthalate 96isophthalate 4 terephthalate 96 isophthalate 4 Outer resin layer HeatHeat Heat TiO2 as Total film Melting point quantity of quantity quantityentire film thickness difference crystalliza- of fusion differenceWhite- [wt %] [μm] among layers tion [J/g] [J/g] [J/g] IV ness Example 120.0 20 — 23 30 7 0.60 84 Example 2 21.4 22 0 27 36 9 0.62 84 Example 320.5 22 0 32 42 10 0.64 84 Example 4 16.4 22 0 32 38 6 0.60 82 Example 516.4 22 0 18 38 20 0.60 82 Example 6 16.4 22 10 32 40 8 0.61 82 Example7 16.4 22 0 30 38 8 0.55 82 Example 8 16.4 22 0 30 38 8 0.90 82 Example9 8.1 42 0 30 38 8 0.61 78 Example 10 16.0 20 0 30 38 8 0.62 80 Example11 16.4 22 0 20 38 18 0.63 82 Example 12 16.4 22 0 32 40 8 0.62 82Example 13 18.0 20 0 30 38 8 0.60 83 Example 14 12.5 20 0 30 38 8 0.6380 Example 15 12.5 20 0 30 38 8 0.63 80 Example 16 12.5 20 0 30 38 80.63 80 Example 17 10.0 20 0 30 38 8 0.63 79 Example 18 12.5 20 0 30 388 0.63 80 Example 19 12.5 20 0 30 38 8 0.63 80 Example 20 15.0 40 0 3038 8 0.60 82 Example 21 16.0 10 0 30 38 8 0.60 82 Example 22 13.3 12 030 38 8 0.60 82 Example 23 16.4 22 0 18 38 20 0.60 82

TABLE 2 Outer resin layer Upper layer Main Another Melting TiO2 Film Waxapplica- Wax addi- component component point amount thickness tionamount Added tion amount [mol %] [mol %] [° C.] [wt %] μm] Wax type[mg/m2] wax type [wt %] Comparative Ethylene Ethylene 238 0 2 Paraffinwax 40 mg/m2 — — Example 1 terephthalate 92 isophthalate 8 ComparativeEthylene 0 256 0 2 Paraffin wax 40 mg/m2 — — Example 2 terephthalate 100Comparative Ethylene Ethylene 247 0 2 Paraffin wax 40 mg/m2 — — Example3 terephthalate 96 isophthalate 4 Comparative Ethylene Ethylene 247 0 2Paraffin wax 40 mg/m2 — — Example 4 terephthalate 96 isophthalate 4Comparative Ethylene Ethylene 238 0 2 Paraffin wax 40 mg/m2 — — Example5 terephthalate 91 isophthalate 9 Comparative Ethylene Ethylene 254 0 2Paraffin wax 40 mg/m2 — — Example 6 terephthalate 98 isophthalate 2Comparative Ethylene Ethylene 247 0 2 Paraffin wax 40 mg/m2 — — Example7 terephthalate 96 isophthalate 4 Comparative Ethylene Ethylene 247 0 2Paraffin wax 40 mg/m2 Stearic acid 0.01 Example 8 terephthalate 96isophthalate 4 Comparative Ethylene Ethylene 247 0 2 Paraffin wax 19mg/m2 — — Example 9 terephthalate 96 isophthalate 4 Comparative EthyleneEthylene 247 0 0.9 Paraffin wax 40 mg/m2 — — Example 10 terephthalate 96isophthalate 4 Outer resin layer Intermediate layer Lower layer FilmFilm Main Another Melting TiO2 thick- Main Another Melting TiO2 thick-component component point amount ness component component point amountness [mol %] [mol %] [° C.] [wt %] [μm] [mol %] [mol %] [° C.] [wt %][μm] Comparative Ethylene Ethylene 238 20 18 Ethylene Ethylene 238 0 2Example 1 terephthalate 90 isophthalate 10 terephthalate 92 isophthalate8 Comparative Ethylene 0 258 20 18 Ethylene 0 256 0 2 Example 2terephthalate 100 terephthalate 100 Comparative Ethylene Ethylene 247 2018 Ethylene Ethylene 247 0 2 Example 3 terephthalate 96 isophthalate 4terephthalate 96 isophthalate 4 Comparative Ethylene Ethylene 236 20 18Ethylene Ethylene 247 0 2 Example 4 terephthalate 91 isophthalate 9terephthalate 96 isophthalate 4 Comparative Ethylene Ethylene 236 20 18Ethylene Ethylene 238 0 2 Example 5 terephthalate 91 isophthalate 9terephthalate 91 isophthalate 9 Comparative Ethylene Ethylene 254 20 18Ethylene Ethylene 254 0 2 Example 6 terephthalate 98 isophthalate 2terephthalate 98 isophthalate 2 Comparative Ethylene Ethylene 247 20 18Ethylene Ethylene 247 0 2 Example 7 terephthalate 96 isophthalate 4terephthalate 96 isophthalate 4 Comparative Ethylene Ethylene 247 20 18Ethylene Ethylene 247 0 2 Example 8 terephthalate 96 isophthalate 4terephthalate 96 isophthalate 4 Comparative Ethylene Ethylene 247 20 18Ethylene Ethylene 247 0 2 Example 9 terephthalate 96 isophthalate 4terephthalate 96 isophthalate 4 Comparative Ethylene Ethylene 247 8 8Ethylene Ethylene 247 0 0.9 Example 10 terephthalate 96 isophthalate 4terephthalate 96 isophthalate 4 Outer resin layer Heat Heat Heat TiO2 asTotal film Melting point quantity of quantity quantity entire filmthickness difference crystalliza- of fusion difference White- [wt %][μm] among layers tion [J/g] [J/g] [J/g] IV ness Comparative 16.4 22 011 36 25 0.63 82 Example 1 Comparative 16.4 22 0 20 42 22 0.63 82Example 2 Comparative 16.4 22 0 16 38 22 0.63 82 Example 3 Comparative16.4 22 11 16 37 21 0.63 82 Example 4 Comparative 16.4 22 2 15 36 210.63 82 Example 5 Comparative 16.4 22 0 21 45 24 0.63 82 Example 6Comparative 16.4 22 0 16 38 22 0.54 82 Example 7 Comparative 16.4 22 016 38 22 0.63 82 Example 8 Comparative 16.4 22 0 16 38 22 0.63 82Example 9 Comparative 6.5 9.8 0 15 38 23 0.60 74 Example 10

TABLE 3 Inner resin layer Film Another component Melting thickness PET[mol %] [mol %] point [° C.] [μm] Example 1 Ethylene terephthalate 86Ethylene isophthalate 14 223 20 Example 2 Ethylene terephthalate 91Ethylene isophthalate 9 236 20 Example 3 Ethylene terephthalate 91Ethylene isophthalate 9 236 20 Example 4 Ethylene terephthalate 90Ethylene isophthalate 10 234 20 Example 5 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 6 Ethylene terephthalate 92Ethylene isophthalate 8 238 20 Example 7 Ethylene terephthalate 92Ethylene isophthalate 8 238 20 Example 8 Ethylene terephthalate 92Ethylene isophthalate 8 238 20 Example 9 Ethylene terephthalate 92Ethylene isophthalate 8 238 20 Example 10 Ethylene terephthalate 92Ethylene isophthalate 8 238 20 Example 11 Ethylene terephthalate 90Ethylene isophthalate 10 234 20 Example 12 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 13 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 14 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 15 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 16 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 17 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 18 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 19 Ethylene terephthalate 94Ethylene isophthalate 6 240 10 Example 20 Ethylene terephthalate 94Ethylene isophthalate 6 240 10 Example 21 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 22 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Example 23 Ethylene terephthalate 94Ethylene isophthalate 6 240 20 Comparative Ethylene terephthalate 90Ethylene isophthalate 10 234 20 Example 1 Comparative Ethyleneterephthalate 96 Ethylene isophthalate 4 247 20 Example 2 ComparativeEthylene terephthalate 90 Ethylene isophthalate 10 234 20 Example 3Comparative Ethylene terephthalate 90 Ethylene isophthalate 10 234 20Example 4 Comparative Ethylene terephthalate 90 Ethylene isophthalate 10234 20 Example 5 Comparative Ethylene terephthalate 89 Ethyleneisophthalate 11 232 20 Example 6 Comparative Ethylene terephthalate 90Ethylene isophthalate 10 234 20 Example 7 Comparative Ethyleneterephthalate 90 Ethylene isophthalate 10 234 20 Example 8 ComparativeEthylene terephthalate 90 Ethylene isophthalate 10 234 9 Example 9Comparative Ethylene terephthalate 90 Ethylene isophthalate 10 234 20Example 10 Inner resin layer Heat quantity Melting point Heat of Heatdifference between quantity of crystallization fusion quantitydifference inner and outer films [J/g] [J/g] [J/g] [° C.] Example 1 3035 5 7 Example 2 36 38 2 4 Example 3 30 35 5 18 Example 4 38 38 0 13Example 5 34 38 4 6 Example 6 34 38 4 7 Example 7 33 38 5 9 Example 8 3338 5 9 Example 9 33 38 5 9 Example 10 33 38 5 9 Example 11 36 38 2 13Example 12 32 38 6 10 Example 13 32 38 6 6 Example 14 32 38 6 7 Example15 34 38 4 7 Example 16 34 38 4 7 Example 17 34 38 4 7 Example 18 34 384 7 Example 19 34 38 4 7 Example 20 28 38 10 7 Example 21 32 38 6 7Example 22 32 38 6 7 Example 23 32 38 6 7 Comparative Example 1 34 38 44 Comparative Example 2 34 38 4 9 Comparative Example 3 34 38 4 13Comparative Example 4 22 30 8 2 Comparative Example 5 28 34 6 2Comparative Example 6 28 30 2 22 Comparative Example 7 26 34 8 13Comparative Example 8 26 34 8 13 Comparative Example 9 26 34 8 13Comparative Example 10 20 34 14 13

For the resin coated metal sheets of Examples 1 to 23 and ComparativeExamples 1 to 10, their formability, surface roughness, corrosionresistance, and adhesion after working were evaluated using the methodslisted below. The evaluation results are listed in Table 4. As listed inTable 4, whereas surface roughness was graded “⊙” or “◯” for the resincoated metal sheets of Examples 1 to 23, surface roughness was graded“x” for the resin coated metal sheets of Comparative Example 1 to 10.Referring to Table 1 and Table 2, for the resin coated metal sheets ofExamples 1 to 23, the outer resin layer is formed of a resin materialwhose difference between the heat quantity of crystallization and theheat quantity of fusion is 20 J/g or less on a unit weight basis. Incontrast, for the resin coated metal sheets of Comparative Example 1 to10, the outer resin layer is formed of a resin material whose differencebetween the heat quantity of crystallization and the heat quantity offusion exceeds 20 J/g on a unit weight basis. This demonstrates that theouter resin layer formed of a resin material whose difference betweenthe heat quantity of crystallization and the heat quantity of fusion is20 J/g or less on a unit weight basis reduces the occurrence ofappearance defects by heat treatment.

(1) Formability

After applying wax to the resin coated metal sheets of Examples 1 to 23and Comparative Examples 1 to 9, a disc with a diameter of 123 mm waspunched to form a shallow drawn can with a drawing ratio of 1.7.Subsequently, redrawing and DI working were performed on this shallowdrawn can with a drawing ratio of 1.3 to form a deep drawn can. Afterforming, scrapes and breakage on the surface of the resin film werevisually observed to give grades in accordance with the standards listedbelow.

Grade “⊙⊙⊙”: No film scrape was observed.Grade “⊙⊙”: A case in which a film scrape developed at a height positionwithin 1 mm of a can flange part.Grade “⊙”: A case in which a film scrape developed at a height positionapart from the can flange part by more than 1 mm and within 5 mmthereof.Grade “◯”: A case in which a film scrape developed at a height positionapart from the can flange part by more than 5 mm and within 15 mmthereof.Grade “Δ”: A case in which a film scrape developed at a height positionapart from the can flange part by more than 15 mm and within 30 mmthereof.Grade “x”: A case in which a film scrape developed at a height positionapart from the can flange part by more than 30 mm or a case in whichbreakage occurred.

(2) Surface Roughness

After applying wax to the resin coated metal sheets of Examples 1 to 23and Comparative Example 1 to 10, a disc with a diameter of 158 mm waspunched to give a shallow drawn can with a drawing ratio of 1.7.Subsequently, redrawing was performed on this shallow drawn can with adrawing ratio of 1.4 to form a deep drawn can. The thus obtained deepdrawn can was heated for 2 minutes in a hot air drying furnace until thecan body temperature became close to the melting point of the film, andthen forcibly cooled by cold air. The state of the outer film aftercooling was visually observed to give grades in accordance with thestandards listed below.

Grade “⊙”: A state in which no black spot was observed.Grade “◯”: A state in which a black spot developed at a height positionwithin 5 mm of a can flange part.Grade “Δ”: A state in which a black spot developed at a height positionapart from the can flange part by more than 5 mm and within 15 mmthereof.Grade “x”: A state in which a black spot developed at a height positionapart from the can flange part by more than 15 mm.

(3) Corrosion Resistance

The resin coating layer of the can flange part of the deep drawn can onwhich heat treatment was performed in the surface roughness evaluationwas scraped to expose the metal sheet. A 5% saline solution was theninjected into the can, and a platinum electrode was immersed into this(the immersing position was at the central part of the can). With theplatinum electrode and the can flange part (a part at which steel sheetis exposed) as the cathode and the anode, respectively, a voltage of 6 Vwas applied between the electrodes, and a current value was read after alapse of 4 seconds. An average value of the current values afterperforming measurement for 10 cans was determined to give grades inaccordance with the standards listed below.

Grade “◯”: A current value of less than 0.1 mA.Grade “Δ”: A current value of 0.1 mA or more and less than 1 mA.Grade “x”: A current value of 1 mA or more.(4) Adhesion after Working

A sample for a peel test (15 mm wide×120 mm long) was cut out from thecan barrel part of the deep drawn can formed in the surface roughnessevaluation. The resin coating layer was partially peeled off from thelong-side edge of the cut-out sample. The peeled resin coating layer wasopened in a direction (at an angle of 180 degrees) opposite the metalsheet from which the resin coating layer was peeled off, and the peeltest was performed with a tensile speed of 30 mm/min to evaluateadhesion per a width of 15 mm in accordance with the standards listedbelow. The surface for which adhesion was measured was on the inside ofthe can.

Grade “⊙”: 1.47 N/15 mm or more (0.15 kgf/15 mm or more).Grade “◯”: 0.98 N/15 mm or more and 1.47 N/15 mm or less (0.10 kgf/15 mmor more and 0.15 kgf/15 mm or less).Grade “x”: Less than 0.98 N/15 mm (less than 0.10 kgf/15 mm).

(5) Evaluation of Whiteness

The whiteness (L-value) of the resin coating layer 3 after resinlamination was measured to evaluate whiteness.

Grade “◯”: The L-value is 75 or more.Grade “x”: The L-value is less than 75.

TABLE 4 Adhesion Forma- Surface Corrosion after bility roughnessresistance Whiteness working Example 1 ◯ ⊙ ◯ ◯ ⊙ Example 2 ◯ ⊙ ◯ ◯ ⊙Example 3 ◯ ⊙ ◯ ◯ ⊙ Example 4 ⊙ ⊙ ◯ ◯ ⊙ Example 5 ⊙⊙ ◯ ◯ ◯ ⊙ Example 6⊙⊙ ⊙ ◯ ◯ ⊙ Example 7 ⊙⊙ ⊙ ◯ ◯ ⊙ Example 8 ⊙⊙ ⊙ ◯ ◯ ⊙ Example 9 ⊙⊙ ⊙ ◯ ◯⊙ Example 10 ⊙⊙ ⊙ ◯ ◯ ⊙ Example 11 ⊙⊙ ◯ ◯ ◯ ⊙ Example 12 ⊙⊙ ⊙ ◯ ◯ ⊙Example 13 ⊙⊙ ⊙ ◯ ◯ ◯ Example 14 ⊙⊙ ⊙ ◯ ◯ ⊙ Example 15 ⊙⊙⊙ ⊙ ◯ ◯ ⊙Example 16 ⊙⊙⊙ ⊙ ◯ ◯ ⊙ Example 17 ⊙⊙⊙ ⊙ ◯ ◯ ⊙ Example 18 ⊙⊙⊙ ⊙ ◯ ◯ ⊙Example 19 ⊙⊙⊙ ⊙ ◯ ◯ ⊙ Example 20 ⊙⊙ ⊙ ◯ ◯ ⊙ Example 21 ⊙⊙ ⊙ ◯ ◯ ⊙Example 22 ⊙⊙ ⊙ ◯ ◯ ⊙ Example 23 ⊙⊙ ◯ ◯ ◯ ⊙ Comparative X X ◯ ◯ ⊙Example 1 Comparative X X ◯ ◯ ⊙ Example 2 Comparative ⊙⊙ X ◯ ◯ ⊙ Example3 Comparative ◯ X X ◯ ⊙ Example 4 Comparative Δ X X ◯ ⊙ Example 5Comparative ◯ X Δ ◯ ⊙ Example 6 Comparative X X ◯ ◯ ⊙ Example 7Comparative ◯ X X ◯ ⊙ Example 8 Comparative ◯ X X ◯ Δ Example 9Comparative X X ◯ X Δ Example 10

INDUSTRIAL APPLICABILITY

We provide resin coated metal sheets in which no appearance defects arecaused by heat treatment.

1-10. (canceled)
 11. A resin coated metal sheet comprising: a metalsheet; a first resin coating layer formed on one main surface of themetal sheet and formed of a resin material whose difference between aheat quantity of crystallization and a heat quantity of fusion afterbeing laminated to the metal sheet is 0 J/g to 20 J/g on a unit weightbasis; and a second resin coating layer formed on another main surfaceof the metal sheet.
 12. The resin coated metal sheet according to claim11, wherein the first and the second resin coating layers are formed ofa resin material containing 90 mol % or more ethylene terephthalateunit, and a melting point of the first resin coating layer is 240° C. to254° C.
 13. The resin coated metal sheet according to claim 11, whereinintrinsic viscosity of the first and the second resin coating layers is0.55 dl/g to 0.90 dl/g.
 14. The resin coated metal sheet according toclaim 11, wherein the first resin coating layer comprises titanium oxidein an amount 8 wt % to 30 wt %.
 15. The resin coated metal sheetaccording to claim 14, wherein the first resin coating layer comprises athree-layer structure of an outermost layer, an intermediate layer, anda lowermost layer, film thickness of the outermost layer and thelowermost layer is 1 μm to 5 and film thickness of the intermediatelayer is 6 μm to 30 μm, and the outermost layer and the lowermost layercomprise titanium oxide in an amount of 0 wt % to 2 wt %, and theintermediate layer comprises titanium oxide in an amount of 10 wt % to30 wt %.
 16. The resin coated metal sheet according to claim 15, whereina difference in melting points among the outermost layer, theintermediate layer, and the lowermost layer is 10° C. or less.
 17. Theresin coated metal sheet according to claim 11, wherein a melting pointof the second resin coating layer is lower than the melting point of thefirst resin coating layer by 4° C. to 20° C.
 18. The resin coated metalsheet according to claim 11, wherein the second resin coating layer isformed of a resin material whose difference between a heat quantity ofcrystallization and a heat quantity of fusion after being laminated tothe metal sheet is 0 J/g to 10 J/g on a unit weight basis.
 19. The resincoated metal sheet according to claim 11, wherein a wax component isapplied to a surface of the first resin coating layer in an adhesionamount of 20 mg/m² to 80 mg/m².
 20. The resin coated metal sheetaccording to claim 11, wherein the first resin coating layer comprises awax component in an amount of 0.05 wt % to 5 wt %.